Genetically modified salmon can breed with wild trout to produce a new fast
growing fish that can harm natural species, scientists have warned.

The researchers fear that plans to farm a new type of GM salmon that grows faster than normal salmon may result in some of the animals escaping into streams and rivers.

They conducted a study to examine the impacts that such an escape would have on natural habitats.

They found that the GM salmon, which have been developed by a Canada firm and are expected to be given approval for sale as food in the US, could mate with wild brown trout.

This resulted in a “hybrid” species that grew faster than even the GM salmon. They also “out competed” wild fish in laboratory based simulation of a stream.

Dr Krista Oke, who led the work at the department of biology at McGill University in Quebec, Canada, said: “To the best of our knowledge, this is the first study demonstrating transmission and ecological consequences from interspecific hybridisation between a GM animal and a naturally hybridising species.

The researchers, whose work is published in the journalProceedings of The Royal Society B, warned that any attempts to farm GM salmon should carefully assess the risks to the wider environment should they escape.

AquaBounty, a Canadian biotechnology firm, has spent 17 years developing a type of Atlantic salmon that will reach full size in half the time of wild salmon.

The "super-salmon" are grown in tanks and Panama and the firm has applied to the Food and Drug Administration, which regulates food in the US, to sell the GM fish in shops.

The FDA recently ruled that meat from the fish was unlikely to pose a threat to human health but it has still to give approval for it to be sold.

The GM fish are unlikely to go on sale in the UK or Europe in the near future as there are strict regulations on the use of GM meat for human consumption.

However, environmental groups have expressed concerns that the fish could escape into the wild and the Atlantic Salmon Federation has said they could disrupt fish ecosystems.

The latest research by Dr Oke and her colleagues seems to support their arguments as the hybrid fish that formed when GM salmon mated with wild trout led to other wild fish being far smaller than they would normally be.

This is because they grew up to 80 per cent faster and ate much of the available food.

Dr Oke added: “Although transgenic hybrids would likely be rarer in the wild than in our experiment, our results indicate that transgenic hybrids have a competitive advantage over salmon in at least some semi-natural conditions.

“If this advantage is maintained in the wild, transgenic hybrids could detrimentally affect wild salmon populations.”

Ron Stotish, chief executive of AquaBounty Technologies, described the research as "encouraging" and insisted would only market sterile female GM salmon, known as AquAdvantage, so they could not breed.

He added: "Brown trout and Atlantic salmon are know to be able to produce hybrid progeny.

"This paper confirms that AquAdvantage, can be used to produce such hybrids, and that the presence of the transgene does indeed confer accelerated growth in hatchery conditions.

“It is worth noting that in 1995, Peter Galbreath and Gary Thorgaard of Washington State University published research that the Atlantic salmon brown trout hybrid is sterile.

"If this holds true, such a hybrid would pose little ecological threat as the fish would not reproduce."